The present invention relates to a biosensor and a measuring apparatus for a biosensor for quantifying and/or detecting existence of a substrate contained in a sample solution.
A biosensor is such a sensor that uses, for a molecule discrimination device, fundamental biological elements such as microbes, enzymes, antibodies, DNAs (deoxyribonucleic acids) and RNAs (ribonucleic acids). More specifically, a biosensor can quantify or detect existence of a substrate contained in a sample solution by utilizing a reaction generated when a substrate is recognized or contacted by a fundamental biological element, for example, such reaction as oxygen consumption by microbial respiration, light emission or enzyme reaction.
Among various biosensors, the commercialization of enzyme sensors, which quantify or detect existence of substrates by using an enzyme and reacting the enzyme with a targeted substrate, has been advanced. For example, enzyme sensors to be used for such targeted substrates as glucose, lactic acid, cholesterol and amino acid are called, e.g., glucose sensor, cholesterol sensor and so forth on the basis of the names of the targeted substrates, and are used for medical measurements, food industry and so on.
According to a measuring system using such enzyme sensor, an electron mediator is reduced by electrons generated, e.g., by the reaction of a certain material (substrate) contained in a sample solution with e.g. an enzyme. The amount of reduction of the electron mediator is electrochemically measured, thereby quantifying the substrate contained in the sample solution.
One of performance capabilities that such biosensor is required to have is capability of conducting the measurement with high accuracy even if the sample solution is in a trace amount. For example, when a patient of diabetes uses a glucose sensor, the sample solution is often a blood taken from the patient. In order to decrease the burden of the patient, it is desired that the amount of blood to be taken from the patient be as small as possible.
Thus, as a biosensor having a capability of conducting measurement even with a trace amount of sample solution, a biosensor of electrode-opposed type is proposed as disclosed in Japanese Laid-open Patent Publication Hei 11-352093. In such proposed biosensor, a working electrode placed on a base plate for the working electrode and a counter electrode placed on a base plate for the counter electrode are opposed to each other with a space therebetween to which a sample solution is supplied. Accordingly, when a voltage is applied between the working electrode and the counter electrode, with the sample solution being supplied to the space, charge transfer between the working electrode and the counter electrode well progresses. Accordingly, measurement with high accuracy becomes possible even with a trace amount of the sample solution.
However, the biosensor of electrode-opposed type has electric connection terminals (which are electrically connected to a driving power supply in a measuring apparatus for a biosensor when the sensor is inserted or mounted in the apparatus) placed on topside and downside of a pair of base plates, respectively, without any specific design. Accordingly, it is difficult for a user to discriminate, e.g. visually, between the topside and downside of the biosensor. Therefore, there is a possibility that the user may insert the biosensor upside down, making a mistake in the top-down side matching of the biosensor with respect to the apparatus. With such wrong insertion of the biosensor, correct measurement cannot be expected.
It is further desired that one measuring apparatus can be used for measuring biosensors corresponding to plural targeted substrates handily without causing wrong insertion of the biosensors. However, it cannot be realized by a conventional biosensor or a combination of a conventional biosensor and a conventional measuring apparatus for a biosensor.